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H Jüppner

Publications and source records attributed to H Jüppner.

124 records · Page 7Linked to original sources
PubMed1980

Adsorption of parathyrin: pitfall for solid phase assays using radiolabelled antibodies?

The physicochemical behaviour of parathyrin on surfaces was investigated. Parathyrin is bound to the wall of polyethylene, polypropylene and flint glass tubes. This adsorptive binding of the hormone, detected by labelled antibodies, is a time-dependent process which is complete within one hour. The addition of plasma decreases but does not prevent adsorption. Coating of the tubes with an anti-N-regional or anti-C-regional antiserum decreases the sensitivity of the detection of 1-34, 53-84 and 1-84 intact parathyrin, when performed in buffer. In the presence of plasma the increase of radiolabelled antibody detecting the parathyrin was more pronounced when tubes were precoated with an anti-parathyrin antibody. The sensitivity of the 1-84 parathyrin assay was also reduced when incubation was carried out in the presence of high concentrations of parathyrin-fragments, calcitonin, somatostatin or bovine serum albumin. Assay specificity seems to be related to the specificity of the labelled antibody for the respective hormonal fragment, not to that of the antibody used for coating the tubes. This investigation illustrates the necessity for the careful control of parathyrin assay conditions, e. g. non-specific binding of native parathyrin and radiolabelled tracers to laboratory reaction vessels.

Adsorption↗
PubMed1979

Binding of bovine parathyroid hormone to surface receptors of cultured B-lymphocytes.

Binding of parathyroid hormone onto B-lymphocytes is detected by the utilization of the labelled antibody membrane assay. The amount of parathyroid hormone bound to the receptor sites was depending on the quantity of cells in the incubation milieu. Each cell line showed typical characteristics in time course of parathyroid hormone binding and maximal receptor capacity. Fragmentation of intact parathyroid hormone, also varying with the cell line tested, was very rapid, even at 24 degrees C. Within 20 min most of the cell lines destroyed 20% of the native hormone in the incubation mixture, indicating a fragmentation rate of up to 2.25 ng/min at 37 degrees C. Bmax and KD for the different lymphocytes was 5.3--19 . 10(11) M and 1.8--18,5 . 10(11) M, respectively. These values are in the range of reported plasma concentrations and may therefore represent more physiological values for the capacity and affinity of membrane receptors.

Animals↗
PubMed1978

Autoantibodies to parathyroid hormone receptor.

Autoantibodies which block the binding of parathyroid hormone to membrane receptors for the hormone were detected in the sera (especially in the IgG fraction) of 49 out of 50 uraemic patients with secondary hyperparathyroidism (patients with high levels of C-regional parathyroid hormone). These antibodies are species-specific. Their presence in the serum in unaffected by dialysis. Inhibition of binding appears to be related to the rise in C-regional parathyroid-hormone levels and the duration of uraemia. The production of cyclic adenosine monophosphate by parathyroid-hormone-stimulated adenyl cyclase was reduced by the blocking antibodies. The findings show that secondary hyperparathyrodism in uraemia is another example of a receptor-antibody disease, but it is not known whether the antibodies act by modifying the affinity of the receptors for the hormone or by reducing the concentration of receptors available.

Animals↗
PubMed1978

Regulation of thyroid hormone metabolism in rat liver fractions.

The nature of the conversion of thyroxine (T4) to triiodothyronine (T3) and reverse triiodothyronine (rT3) was investigated in rat liver homogenate and microsomes. A 6-fold rise of T3 and 2.5-fold rise of rT3 levels determined by specific radioimmunoassays was observed over 6 h after the addition of T4. An enzymic process is suggested that converts T4 to T3 and rT3. For T3 the optimal pH is 6 and for rT3, 9.5. The converting activity for both T3 and rT3 is temperature dependent and can be suppressed by heat, H2O2, merthiolate and by 5-propyl-2-thiouracil. rT3 and to a lesser degree iodide, were able to inhibit the production of T3 in a dose related fashion. Therefore the pH dependency, rT3 and iodide may regulate the availability of T3 or rT3 depending on the metabolic requirements of thyroid hormones.

Animals↗
PubMed1978

Endocrinological aspects of PTH metabolism in the kidney.

Various methods for the measurement of intact PTH, PTH fragments and PTH binding to receptors were applied to clarify the role of renal receptors for the bioexpression of PTH. Glomerular receptors may contribute approximately 20% of the renal PTH catabolism. PTH also binds to tubular receptors at the luminal side (brush border membranes) as well as at the antiluminal site (basal-lateral membrane). Scatchard plot analysis of PTH binding to these receptors allows the calculation of an equilibrium dissociation constant and binding capacity, if correction is made for inactivation of bioactive PTH (measured by LAMA). Binding to receptors is--in our systems--invariably associated with degradation of the intact hormone to N-terminal and C-terminal fragments of different molecular weight. Antibodies against basal lateral membranes and against brush border membranes are able to inhibit PTH binding to tubular membranes. Sera of uremic patients with inappropriately high PTH contain a globulin which interferes with PTH binding to the receptor, suggesting that uremia may be another example for a "hormone receptor antibody disease".

Animals↗
PubMed1978

Kinetics of PTH metabolism and PTH fragments in chronic renal failure.

Distribution and metabolic degradation of bPTH was studied in man after infusion of 400 U bPTH and blood sampling up to 2h. Disappearance rates of intact 1-84 bPTH, carboxyl- and amino-regional peptides were calculated for healthy subjects (n = 12); patients suffering from moderate (GFR 15--30 ml/min, n = 4) and advanced (GFR less than or equal to 10 ml/min, n = 36) chronic renal failure; and bilateral nephrectomized patients (n = 3). Two components with a rapid and a slow disappearance rate can be separated ("distribution", "metabolism"). Half-lives are found to be in the range known from animal experiments with marked differences between intact 1-84 PTH and peptide fragments. Influence of impaired renal function on metabolic turnover rates of PTH is given.

Alkaline Phosphatase↗
PubMed1977

TBG-dependency of age related variations of thyroxine and triiodothyronine.

Thyroxine (T4), triiodothyronine (T3) and thyroxine-binding globulin (TBG) were determined in healthy individuals ranging in age from newborn to 95 years. T4: 10.25 +/- 1.62 microng/100 ml, T3: 1.62 +/- 0.35 ng/ml and TBG: 1.34 +/- 0.15 mg/100 ml, were found elevated until puberty compared to a middle age group with T4: 7.27 +/- 2.26 microng/100 ml, T3: 1.15 +/- 0.24 ng/ml and TBG: 0.98 +/- 14 mg/100 ml. T4 and T3 followed almost TBG concentration. In old age is dissociation between T4: 5.79 +/- 1.56 microng/100 ml, T3: 0.79 +/- 0.21 ng/ml and TBG: 1.28 +/- 0.15 mg/100 ml was found. Except for old age the ratio T4/TBG and T3/TBG minimized the age dependent variation of T4 and T3 and reduced the coefficient of variance from 26% to 17.7% for T4 and from 26.5 to 25% for T3. Age reduction of T4/TBG is 15% and of T3/TBG 13% respectively more pronounced than for T4 and T3 alone. These data indicate: 1) age related variations of T4 and T3 due to age dependency of TBG, 2) deviation of T4 and T3 values in old age from that expected by their TBG levels and 3) the importance of the routine use of hormone/TBG ratio.

Adolescent↗
PubMed1976

The stimulation of growth hormone release by ACTH and its inhibition by somatostatin.

The rapid injection of 0.5 or 1.0 mg of tetracosacitid (Synacthen¿) was followed by a distinct increase of plasma growth hormone (GH) within 30 or 45 min in 5 of 7 normal volunteers. A second control test was performed in 3 of the 5 "responders" and 1 "non-responder" and showed a consistent reaction in all of them. The tests were then repeated in the 5 "responders" during an infusion of somatostatin (150 mug/h) and the GH response was totally abolished (3 subjects) or markedly reduced (2 subjects). Thus the ACTH induced GH release behaves in a manner similar to most other physiological or pharmacological stimuli of GH release. The cortisol output after ACTH was not altered by somatostatin.

Adrenocorticotropic Hormone↗
PubMed1976

[Calculation of radioimmunochemical determinations by "spline approximation" (author's transl)].

A simplified method, based on the "spline approximation", is reported for the calculation of the standard curves of radioimmunochemical determinations. It is possible to manipulate the mathematical function with a pocket calculator, thus making it available for a large number of users. It was shown that, in contrast to the usual procedures, it is possible to achieve optimal quality control in the preparation of the standard curves and in the interpolation of unknown plasma samples. The recaluculation of interpolated values from their own standard curve revealed an error of 4.9% which would normally be an error of interpolation. The new method was compared with two established methods for 8 different radioimmunochemical determinations. The measured values of the standard curve showed a weighting, and there was a resulting quality control of these values, which, according to their statistical evalution, were more accurate than those of the others models (Ekins et al., Yalow et al., (1968), in: Radioisotopes in Medicine: in vitro studies (Hayes, R. L., Goswitz, F.A. & Murphy, B. E. P., eds) USA EC, Oak Ridge) and Rodbard et al. (1971), in: Competitive protein Binding Assys(Odell, W. D. & Danghedy, W. H., eds.) Lipincott, Philadelphia and Toronto). In contrast with these other models, the described method makes no mathematical or kinetic preconditions with respect to the dose-response relationship. To achieve optimal reaction conditions, experimentally determined reaction data are preferable to model theories.

Computers↗
PubMedDate not supplied

Homologous radioimmunoassay for human mid-regional parathyroid hormone.

A radioimmunoassay, selective for the clinically important mid region of human parathyroid hormone (hPTH), is reported. The synthetic 44-68 amino acid sequence (h44-68PTH) was used as both the standard and tracer material. This eliminated many of the undesirable characteristics associated with PTH assays the employ hormone of biological origin. These components allowed the detection of mid regional fragments present in both intact and fragmented hPTH, with a working range between 50 and 2500 pg/ml h44-68PTH. There was no interference from serum proteins and no significant cross reactivity to a range of N-terminal, C-terminal and other mid regional hPTH peptides. The assay proved to be rapid (total time 24 h) and was extremely reproducible, with an intraassay and interassay variation of 2.8% and 5.6% respectively (expressed as percentage SE in mean). The plasma concentration of normal subjects was established as 129 +/- 6 pg/ml (h44-68PTH) with a range of 50-300 pg/ml (n = 42). This assay, using fully synthetic hPTH peptides, was able to distinguish between euparathyroid and hyperparathyroid subjects, which suggests that the assay is of diagnostic value.

Amino Acid Sequence↗
PubMedDate not supplied

Inhibition of renal adenylate cyclase by plasma from uremic patients.

The native plasma of patients suffering from renal insufficiency inhibited the parathyroid hormone (PTH), the vasopressin (VP) and the NaF-activated adenylate cyclase (AC) in bovine renal plasma membranes. A crude immunoglobulin fraction, prepared by (NH4)2SO4 precipitation, decreased only the hormone, but not the NaF activated AC. Chromatography of the native plasma on a AcA 34 column revealed two peaks inhibiting the PTH and to a lesser extent the VP dependent AC. Only the second peak reduced the NaF stimulated cAMP production. None of the column samples inhibited the isoproterenol stimulated adenylate cyclase in turkey red blood cells. Further purification of the first peak on a Sepharose 6B column confirmed previous results that immunoglobulins may block the PTH receptor in the kidney. Repurification of the second peak of inhibition on a Bio-Gel P10 column suggested that small peptides crossreacting in the radioimmunoassay for PTH may desensitize the hormonal receptor.

Adenylyl Cyclase Inhibitors↗
PubMedDate not supplied

Properties of amino-terminal parathyroid hormone-related peptides modified at positions 11-13.

Biological properties of amino-terminal PTHrP analogues modified in the region 11-13 were examined using ROS 17/2.8 cells. [Leu11,D-Trp12,Arg13,Tyr36]PTHrP(1-36)amide had a 17-fold lower binding affinity for the receptor (apparent Kd: 5 x 10(-8) M) than [Tyr36]PTHrP(1-36)amide or [Arg11,13,Tyr36]PTHrP(1-36)amide (apparent Kd for both: 2 x 10(-9) M). Moreover, it is only a weak partial agonist despite completely inhibiting radioligand binding. [Leu11,D-Trp12,Arg13,Tyr36,Cys38]PTHrP(7-3 8) and PTHrP(7-34)amide had similar receptor affinities (apparent Kds: 5 x 10(-8) M and 8 x 10(-8) M), while that of [Nle8,18,Tyr34]bPTH(7-34)amide was more than 10-fold lower (apparent Kd: 2 x 10(-6) M). These changes in biological properties suggest that high affinity receptor binding requires both amino- and carboxyl-terminal domains of the PTHrP(1-36) sequence and/or intramolecular interactions which are impaired by the D-Trp substitution for Gly12.

Amino Acid Sequence↗
PubMedDate not supplied

In situ localization of PTH/PTHrP receptor mRNA in the bone of fetal and young rats.

We characterized cells that express parathyroid hormone/parathyroid hormone related peptide (PTH/PTHrP) receptor mRNA in bones of fetal and postnatal rats by in situ hybridization. During endochondral development of fetal bones, PTH/PTHrP receptor transcripts were highly expressed both in maturing chondrocytes and in osteoblasts in the periosteum and ossification center, but not in fully hypertrophic chondrocytes. Similar to the localization in the fetal bones, PTH/PTHrP receptor mRNA expression was highly localized to maturing chondrocytes in the articular cartilage and growth plate, and to osteoblasts in the femur of young rats. In both young and fetal rats, transcripts for Type X collagen were localized to hypertrophic chondrocytes, mostly between chondrocytes and bone cells both of which express PTH/PTHrP receptor mRNA. Transcripts for PTH/PTHrP receptors and alkaline phosphatase co-localized in the bone of young rats, but they did not co-localize in fetal bones at the early stages of endochondral ossification. These results show that PTH/PTHrP receptor mRNA is expressed in a cell-type and stage-specific manner during skeletal development.

Animals↗